This invention relates to paper products having a unique coating thereon rendering them well suited for use with ink jet printers.
Advances in ink jet printing technology have placed new demands on the printed paper and paper coatings. To function properly the printed substrate must quickly absorb the ink and ink vehicles directly after printing, maximize the ink optical density, minimize ink bleed and wicking, and provide a means of making the inks waterfast.
Ink jet coatings generally comprise silica pigment having a high absorption capability and a polymeric binder such as a poly(vinyl alcohol) binder having a high binding strength. A variety of additives have been utilized to improve coating properties. Cationic additives, for example, have been added to help with ink waterfastness and lightfastness. Other variations in the ink jet coating formulations include the use of non silica pigments such as clays, aluminum hydrate, calcium carbonate, titanium dioxide, magnesium carbonate and the use of binders such as styrene-butadiene, poly(vinyl pyrrolidone), polyvinyl acetate, acrylic binders, and starch.
The following patents and articles are representative of various resins and ink jet paper coatings.
U.S. Pat. No. 4,818,341 discloses the addition of a cationic polymer e.g. hydrolyzed vinyl acetate or vinyl propionate/N-vinyl formamide copolymers to paper stock to enhance the dry-strength in all types of paper and paper board, e.g., writing paper and packaging papers. The polymers are added in an amount of from 35-150 grams per square meter for paper and up to 600 grams per square meter for paper board.
U.S. Pat. No. 4,880,497 discloses the addition of water-soluble copolymers containing polymerized vinyl amine units, e.g., a hydrolyzed vinyl acetate/N-vinyl formamide copolymer to paper stock prior to sheet formation in an amount of from 0.1-5% based on dry fiber.
Japanese-laid open Kokai application 5-278323 discloses a recording sheet having good ink absorptivity, image quality and excellent water resistance which comprises a dye fixing layer and ink adsorption layer laminated thereon. One of the principal components of the dye fixing layer applied to the recording sheet is a cation modified polyvinyl alcohol. Cation modified polyvinyl alcohols are characterized as hydrolyzed copolymers of vinyl acetate and ethylenically unsaturated monomers having quaternary ammonium salt groups. The content of the cationic group is from 0.1-10 mole percent.
An abstract, of Japanese 63162276A2 discloses an image acceptor for ink jet recordings. The image acceptor includes silica pretreated with water soluble resins either on the recording surface or within the acceptor. A solution of sodium silicate and sulfuric acid is mixed with 5% of a cation modified polyvinyl alcohol and applied to a paper sheet and then an ink applied thereto.
Japanese Patent 05139023 discloses an aqueous based ink jet coating comprising silica pigment and a fully hydrolyzed, medium molecular weight poly(vinyl alcohol) coating. This coating is applied to a paper support at coat weights of 0.7 to 0.8 g/cm2 to provide high color quality images with good dot shape.
German patent 514633 A1 921125 describes an ink jet coating which contains 50% silica pigment, 40% poly(vinyl alcohol) having a hydrolysis value of 92.5%, and 10% of a cationic polyacrylamide. When applied to a paper substrate at a coating weight of 10 grams/m2, this coating provides excellent color density and small dot diameters yielding excellent print fidelity.
Japanese patent 01186372 A2 890725 describes the addition of polyacrylamide to an ink jet coating comprising silica pigment and fully hydrolyzed low molecular weight poly(vinyl alcohol). This coating yield good smudge resistance and lightfastness.
Japanese patent 06247036 A2 940906 discloses the use of a cationic polyethyleneimine quaternary ammonium salt in combination with silica pigment and fully hydrolyzed low molecular weight poly(vinyl alcohol) as an ink jet receiving layer.
Japanese patent 61134291 A2 860621 discloses a cationic PVOH binder for use in an ink jet coating; the binder used is a saponified trimethyl-3-(1-acrylamidopropyl)ammonium chloride-vinyl acetate copolymer with a percent hydrolysis of 98.5 and a cationic content of 3 mole % and a degree of polymerization of 1750. Coatings using this binder with silica pigment provide excellent print fidelity and good water resistance to paper.
U.S. Pat. No. 5,405,678 discloses an ink jet paper having a substrate coated with a non coalesced latex film comprised of a hydrophobic polymer, e.g., ethylene-vinyl chloride copolymers, acrylic latexes, silica, and dispersants.
U.S. Pat. No. 5,270, 103 discloses receiver sheets suited for printing with aqueous based inks, such as those used in ink jet printing systems. The coating formulation is comprised of a pigment and a binder consisting of polyvinyl alcohol and another polymer, e.g., cationic polyvinyl alcohol and poly(vinyl pyrrolidone).
U.S. Pat. No. 6,096,826 discloses the synthesis of a amine functional polyvinyl alcohol via the reaction piperidone with poly(vinyl alcohol) particles. The end product was found to be useful as a mordant/binder for ink jet coated papers.
U.S. Pat. No. 6,096,440 discloses the use of an ink jet recording medium having an ink receiving layer composed of hydrophilic resin, a block copolymer of polyvinyl alcohol and a hydrophobic polymer. US ""440 further discusses the use of a cationic-modified poly(vinyl alcohol), Kurray CM-318, produced by Kuraray Co. Ltd. as a binder for the ink jet receiving layer.
This invention relates to an improvement in paper products having an aqueous based ink jet coating applied to its surface. The improvement generally resides in the incorporation of an a primary amine functional polyvinyl alcohol (PVOH/NH2) as a polymeric binder in the ink jet coating. One form of an amine functional polyvinyl alcohol is produced by the hydrolysis of a copolymer of vinyl acetate and N-vinylformamide (PVOH/PVNH2), another formed by the polymerization of vinyl acetate and allyl amine, and another is the 4-aminobutyral derivative of polyvinyl alcohol.
Several advantages are associated with the paper products incorporating the improved ink jet coating. These advantages include:
the incorporation of a primary amine functional polyvinyl alcohol as a polymer binder in the ink jet coating eases the makedown procedure of the coating formulation by eliminating the need to add cationic materials;
the addition of a primary amine functional polyvinyl alcohol provides excellent binding strength with the silica pigments used in ink jet coatings;
the addition of a primary amine functional polyvinyl alcohol provides excellent ink optical density with regard to monochrome black, composite black, and primary colors;
the addition of a primary amine functional polyvinyl alcohol provides excellent waterfastness to the printed inks;
the addition of a primary amine functional polyvinyl alcohol provides for excellent lightfastness of the inks;
the addition of a primary amine functional polyvinyl alcohol provides for excellent rheological response in terms of shear thickening response when used in conjunction with silica pigment thereby helping the paper coater achieve a greater coating solids level which can allow for higher coat weights and increased production speeds; and
the addition of a primary amine functional polyvinyl alcohol provides excellent ink dry time after printing onto the coated ink jet paper.
Typically, a primary amine functional polyvinyl alcohol is selected from the group consisting of: hydrolyzed copolymers of vinyl acetate and N-vinylamide, a hydrolyzed copolymer of vinyl acetate and allylamine, and primary aminoalkylal derivatives of polyvinyl alcohol.